Cutting illumination on front of stage (9)
I believe the answer is:
slighting
'cutting illumination on front of stage' is the definition.
Although both the answer and definition are present participle verbs, I can't see how one could define the other.
'cutting illumination on front of stage' is the wordplay.
'cutting' means to remove the last letter.
'illumination' becomes 'light' (synonyms).
'on' is an insertion indicator.
'front of stage' becomes 'sting' (I can't justify this - if you can you should believe this answer much more).
'light' with its last letter taken off is 'ligh'.
'ligh' going within 'sting' is 'SLIGHTING'.
Can you help me to learn more?
(Another definition for slighting that I've seen is " Insulting (someone) by inattention".)